The erection at Cairo, Egypt, of a monument to L. P. Mouillard, recalls attention to one of the greatest missionaries of the flying cause which the nineteenth century produced. Mouillard was a Frenchman who passed a large part of his life in Algeria and Egypt, where his attention was attracted, by the wonderful soaring of vultures on fixed wings. His imagination was greatly excited by what he saw, and during the remainder of his life he was like a prophet crying in the wilderness, exhorting the world to repent of its unbelief in the possibility of human flight.In 1881 he published a book called “The Empire of the Air,” which is one of the most remarkable pieces of aeronautical literature that has ever been published.